Which one of the following is not a form of literature for children?

A thesaurus is a reference book that lists synonyms and antonyms — it is a vocabulary reference tool, not a form of literature. Picture books, myths and legends, and tales of historical heroes are all narrative or literary forms specifically suited for children, engaging their imagination through stories. A thesaurus, however, is a lexical reference work with no narrative or literary form, and hence is not a form of children's literature.